Solar Thermal Heating
Conventional water heaters can be very polluting. In fact, the average family of four contributes approximately two tons of CO2 emissions each year through conventional water heating. Although solar hot water systems cost more than electric or gas heaters, once the solar systems are installed utility costs are often dramatically reduced.
A solar water heating system consists of solar panels connected to a building’s existing water heating system. It is one of the most inexpensive renewable energy systems to install and has a fast economic payback.
How it works: A flat-plate collector is the most common, which consists of an insulated aluminum box with tempered glass on the front. Ablack plate with a grid of copper pipes attached to it is behind the glass, and a non-toxic antifreeze mixture fills the collectors and all the piping. When the sun shines onto the collectors, the mixture heats up, and a pump circulates the mixture from the collectors to a heat exchanger. The heat exchanger transfers the heat from the mixture to water used for domestic uses, or it can also be used as a space heating system.
Link to the US Department of Energy's website on Solar Thermal Heating
Photovoltaics (PV), or solar electric systems, use the sun’s energy to create electricity.
How it works: Photovoltaics are a semiconductor technology that convert light energy into electrical energy. Photons from the sun strike the face of a solar cell, which is made of two layers (silicon and boron or phosphorus). Photons knock off electrons in the base layer and bounce it to the upper silicon layer. The electrons travel through a wire from the top layer to an inverter, then return to the bottom layer of the solar cell where they begin journey once again. An inverter converts electricity from direct current (DC) to utility grade alternating current (AC).
When using photovoltaics, wind or a hybrid (PV and wind) system for electrical generation, there are three approaches to system design:
1) Off-Grid Independent System
There is no connection to utility lines, and is most practical in isolated locations. A set of batteries store electricity. This system will frequently make use of more than one resource. A gasoline generator is sometimes used for an emergency backup.
2) Grid-Connected System
This provides the benefits of renewable energy and the consistency of the utility. Utilities allow “net metering,” which enables surplus power to be sent back to the grid, and power to be drawn from the grid when more electricity is needed. This is a clean design, however
when the grid is “down,” no power is available.
3) Grid-Connected Battery-Backed System
This type of system provides power when the utility fails by adding a set of batteries on site to a gridconnected system. This configuration is most practical when an uninterruptible power supply is required.
Link to the US Department of Energy's website on generating your own Solar Electricity